Electric contact assemblage of contact fingers in which helically wound conductive members provide contact pressure



March 31, 1964 K. H. DATE 3,127,492

ELECTRIC CONTACT ASSEMBLAGE 0F CONTACT FINGERS IN WHICH HELICALLY wouun CONDUCTIVE MEMBERS PROVIDE CONTACT PRESSURE Filed May 29. 1961 2 Sheets-Sheet 1 IN VEN TOR.

fi zw HENRY D475 March 31, 1964 K. H. DATE 3,127,492

ASSEMBLAGE OF CONTACT FINGERS ELECTRIC CONTACT IN WHICH HELICALLY WOUND CONDUCT MEMBERS PROVIDE CONTACT PRESSU Filed May 29 1961 2 Sheets-Sheet 2 11v VEN TOR.

Hqzuo F/E/vm D475 United States Patent Ofiice 3,127,492 Patented Mar. 31, 1964 ELECTRIC CONTACT ASSEMBLAGE F CONTACT FINGERS IN WHICH HELICALLY WOUND CUNDUCTIVE MEMBERS PROVIDE CONTACT PRESSURE Kazuo Henry Date, South Milwaukee, Wis., assignor to McGraw-Edison Company, Milwaukee, Wis., a corporation of Delaware Filed May 29, 1961, Ser. No. 113,224 Claims. (Cl. 200-166) This invention relates to electrical contacts and, more particularly, to an electric switch contact assembly for making and breaking an electric circuit in cooperation with a complementary contact.

In high speed electric switches wherein a movable contact rod or blade engages stationary contact structure with great force, the impact may cause the movable contact member to rebound or bounce slightly. In addition, when the stationary contact structure comprises contact fingers or the like which are biased toward engagement with the movable contact member when it is in its closed position, these fingers may also experience some bounce during high speed closing. Such contact bounce can cause a momentary parting between the stationary contact and the movable contact member so that an arc will be struck therebetween.

In addition, it is preferable that the fixed and movable contact members of a switching device have mounting structure which permits self-alignment to compensate for wear and normal manufacturing tolerances. Because of the contact bounce problem and the necessity for selfalignment, the stationary contact members in prior art switching devices required complicated and expensive mounting assemblies.

It is an object of the invention to provide new and improved contact structure in which manufacture and assembly is greatly facilitated.

A further object of the invention is to provide contact structure or a high speed switching device in which the eifect of contact bounce associated with the high speed engagement or disengagement of the cooperating contact elements is eliminated.

Another object of the invention is to provide contact structure having a plurality of contact fingers in which helically wound conductive members provide contact pressure, hold the contact fingers in position and also provide current interchange between the contact fingers and their supporting structure.

Yet another object of the instant invention is to provide contact structure for an electrical device which is self-adjusting for wear and misalignment without loss of contact pressure.

These and other objects and advantages of the instant invention will become more apparent from the detailed description of the invention taken with the accompanying drawings in which:

FIG. 1 is a side elevational view, partly in section, of a preferred embodiment of the instant invention;

FIG. 2 is a view taken along lines 22 of FIG. 1;

FIG. 3 is a side elevational view, partly in section, of an alternate embodiment of the instant invention;

FIG. 4 is a side elevational View of the contact structure of FIG. 3 with parts broken away; and

FIG. 5 is a view taken along lines 5-5 of FIG. 4.

In general terms, the invention comprises a contact assembly comprising a plurality of complementary contact fingers engageable at one end to a mounting memher and at their other ends by a movable contact member. A housing surrounds the contact fingers and is spaced therefrom. Helically wound conductive current interchange members are disposed in grooves between the housing and the contact fingers for transferring current therebetween and for providing high pressure engagement with the movable contact member. The distance across the gap between the housing and the contact fingers is less than the outside helical diameter of the spring convolutions so that they are forced to lay over with spaced apart points on each convolution in firm frictional engagement with the housing and the contact fingers.

As shown in FIGS. 1 and 2, the novel contact assembly, designated generally by the reference numeral 10, is adapted to cooperate with a movable contact element 11 to close an electric circuit. It will be appreciated that contact element 11 may be actuated vertically by any suitable switch operating mechanism, not shown.

The contact assembly 10 includes a housing 12 and a. plurality of contact fingers 14 which are mounted therein. Housing 12 is generally cup-shaped and has a cylindrical sidewall 15 and a planar base portion 16. The housing 12 is mounted on suitable supporting structure, such as a cylindrical stud 18, by a bolt 29 whose threaded body portion 21 passes through an aperture '22 formed in the base portion 16 and which is threadably received in a coaxial tapped hole 24 in the stud 218. As seen in FIG. 1, the head 25 of bolt 29 has a curved lateral surface against which the upper end of each of the contact fingers 14 are mounted.

The contact fingers 14 consist of four elongate, arcuate-in-cross section, conductive segments which are disposed in spaced apart circular array within housing 12 to provide a tulip-type contact jaw for receiving the cylindrical moving contact element '11. The inner face of each segment 14 comprises an upper surface 26 which is cylindrical and which engages the .arcuate head 25 in substantially circular line contact. The lower portion of each of the inner faces of the contact fingers 14 comprises a pair of substantially planar surfaces 2 8 which intersect at an obtuse angle so that each of the contact fingers '14 will engage the movable contact element 11 at a least two points. The contact fingers 14 are prevented from moving out of the housing 15 by a laterally extending lug 29 integrally formed at the extreme upper end of each and which engages a groove fail in the base of the head 25 of bolt 20.

The current interchange structure for transferring current from the contact fingers 14 to the housing 12 includes a pair of parallel, longitudinally directed, spaced-apart grooves 31 formed in the outer surf-ace of each of the contact fingers 14. In addition, a helically wound linear conductive current interchange member 34 is disposed in the gap between each of the grooves 3 1 and the inner surface 35 of the housing 12. As shown particularly in FIG. 1, the outside helical diameter of each of the current interchange members '34 is larger than the distance between the lower portion of its respective groove 31 and the surface 35. Thus the individual convolutions of the spring 34 are forced to lay over at an angle relative to their helical axis. As a result, the resiliency of each of the current interchange members 34 holds their convolutions in firm high pressure engagement with the housing 12 and each of the fingers 14. In addition, the spring contact members 34 hold the upper cylindrical surfaces of each of the contact fingers 14 in resilient rocking engagement with the arcuate surface of head 25. The lower portion of spring current interchange members 34 will also hold each of the surfaces 28 of contact fingers 14 in high pressure engagement with the movable contact member 11 when the latter is in its closed position as shown by phantom lines in FIG. 1.

It will be appreciated that when movable contact 11 is in its closed position, the current path through the contact structure is from the movable contact 11, through the contact fingers 14, the current interchange springs 34, the housing 12, and to the base member 18-. Thus it is preferable that each of the contact fingers 14 of housing 12, the base member 18, as well as each of the current interchange springs 34, be composed of a suitable conductive material. In order to prevent scarring of the contact fingers 14 due to arcing which may occur during a switch opening operation, an insert member 36 of an are resistant material, such as copper-tunsten alloy, is provided at each of the lower ends of said contact fingers.

'In assembly of the structure just described, the housing 12 is first secured to conductive member 18 by bolt The current interchange springs 34 are then placed therein and each of the contact fingers '14 are inserted through the lower end of housing 12 which necessitates merely loeating the contacts 34 and laying them over. After the last contact finger 14 has been inserted, an insulating washer 38 is placed in a recess 39 formed in the lower end of the cylindrical portion 15 of housing 12 and is secured in this position by a metallic ring 40. This prevents longitudinal movement of the springs 34 out of the housing 12.

It can be seen from the foregoing discussion that the spring contacts 34 not only provide a current interchange path between the contact fingers 14 and the housing 12 but also provide a resilient support for said fingers. As a result, they are able to absorb the impact of a high speed closure thereby substantially limiting the tendency for the rod 11 to rebound or bounce. In addition, the resilient support of the contact fingers 14 allows a substantial degree of misalignment to exist in the contact rod 11 without appreciable loss in contact pressure between the rod 11 and the fingers 14. Also, because the fingers 14 are resiliently urged into engagement with the rod I11 there is automatic compensation for wear in these members.

FIGS. 3, 4 and 5 show an alternate embodiment of the instant invention in which springs 34' have an annular configuration and are disposed in concentric grooves formed in the inner surface of the housing 12' and the outer surfaces of the contact fingers 14. More specifically, a pair of parallel, axially spaced apart grooves 40' are formed in the inner surface of the cylindrical portion of housing 12'. In addition, a pair of parallel, spaced apart, arc-shaped grooves 42 are formed transversely across the outside surface of each of the contact fingers 14 to provide a pair of parallel, substantially annular grooves which are concentrically disposed relative to the grooves 40. In this embodiment, the current interchange members 34' have an annular configuration and are disposed in the gaps between the grooves 40 and 42. As seen particularly in FIG. 5, the outside helical diameter of each of the current interchange members 34' is larger than the distance between the lower portions of the grooves '40" and 42. As a result, the contact members 34' are forced to lay over at an angle relative to their helical axis. The resiliency of the current interchange members 34' hold each of their convolutions in high pressure engagement with each of the grooves 40 and 42. Also, the upper member 34' holds the upper end of the contact fingers 14 in resilient rocking engagement with the head of bolt 20 while the lower spring member 34 holds each of the surfiaces 28 in high pressure engagement with the movable contact member 11 when it is in its closed position as shown FIG. 4.

As seen in the drawings, the sidewalls of each of the grooves 40' and 42 are flared outwardly. As a result, each of the convolutions of current interchange springs 34 will contact each of the grooves 40' and 42 at at least two points. This provides a pair of current interchange paths through each of the convolutions of spring 34 between the grooves 40 and 42. It will be noted, too, that the contact fingers 14 in the embodiment of FIGS. 3-5 are not anchored to the bolt 20". This is possible because the springs 34' act to retain the contact fingers 14' within the housing 12.

While only a few embodiments of the instant invention have been shown and described, it is not intended that the invention be limited thereby, but only by the scope of the appended claims.

I claim:

1. A contact assembly comprising a plurality of elongate contact fingers, said contact fingers each having a contact surface on one side thereof, certain of said con tact fingers being disposed with their contact surfaces in an opposed relation to each other for receiving an elongate contact therebetween, a conductive member disposed in spaced relation from the opposite sides of each of said contact fingers, ia helically wound resilient current interchange spring disposed the gap between each of said contact fingers and said conductive member, the axis of said springs being parallel to the longitudinal axis of said contact fingers, the outside convolutional diameter of each of said springs being greater than the distance across said gap so that each of said springs are forced to lay over with their individual convolutions inclined relative to their helical axis, the inherent resiliency of said springs holding each of their individual convolutions in firm trictional engagement with their associated contact fingers and said conductive member, whereby a plurality cf urrent interchange paths are provided across said gaps and said contact fingers are urged into high pressure electrical engagement with said contact rod.

2. A contact assembly comprising a plurality of elongate contact fingers disposed in a substantially circular array for receiving an elongate contact rod, a conductive member surrounding said contact fingers and spaced therefrom, a longitudinal groove formed in each of said fingers and opening toward said conductive member, a helically wound resilient current interchange spring disposed in each of the gaps between said grooves and said conductive member, the outside convolutional diameter of each of said springs being greater than the distance between said grooves and said conductive member so that each of said springs are forced to lay over with their individual convolutions inclined relative to their helical axis, the inherent resiliency of said springs holding each of their individual convolutions in firm frictional engagement with their associated contact fingers and said conductive member, whereby a plurality of current interchange paths are provided across said gaps and said contact fingers are urged into high pressure electrical engagement with said contact rod.

3. A contact assembly comprising a plurality of elongate contact members, said contact members each having a contact surface on one side thereof, said contact members being disposed with their contact surfaces in a circular array for receiving an elongate contact rod therebetween, a conductive member surrounding said contact members and spaced from the opposite sides thereof, a plurality of longitudinal grooves formed in each of said opposite sides and opening toward said conductive member, a helically wound resilient current interchange spring disposed in the gap between each of said grooves and said conductive member and extending for a substantial portion of the length of said contact members, the axis of each of said springs being substantially parallel to the longitudinal axis of said contact members, the outside convolutional diameter of each of said springs being greater than the distance across said gap so that each of said springs are forced to lay over with their individual convolutions inclined relative to their helical axis, the inherent resiliency of said springs holding each of their individual convolutions in firm electrical engagement with their associated contact members and said conductive member, whereby a plurality of current interchange paths are provided across said gaps and said contact members are urged into high pressure electrical engagement with said contact rod.

4. A plurality of elongate contact fingers disposed in a circular array, a conductive member surrounding said contact fingers and. spaced therefrom, said conductive member and said contact fingers comprising a contact assembly open at one end, an elongate circular-in-crosssection contact rod constructed and arranged for movement into and out of the open end of said contact assembly, groove means formed in said contact fingers and opening toward said conductive member, helically wound resilient current interchange spring means disposed in the gap between said groove means and said conductive member, the outside convoiutional diameter of said spring means being greater than the distance between said groove means and said conductive member so that said spring means is forced to lay over with its individual convolutions inclined relative to its helical axis, the inherent resiliency of said spring means holding its individual convolutions in firm electrical engagement with said fingers and said conductive member, whereby a plurality of current paths are provided across said gap and said contact fingers are urged into high pressure electrical engagement with said contact rod, a circular-in-cross-section spacer member disposed between said contact fingers in the other end of said contact assembly, said spacer member and said contact rod supporting said contact fingers in substantial parallelism to insure uniform contact pressure between said spring means and said contact fingers and said conductive member at both ends of said assembly.

5. A plurality of elongate contact fingers disposed in a substantially circular array, a conductive member surrounding said contact fingers and spaced therefrom, said conductive member and said contact fingers comprising a contact assembly open at one end, an elongate circularin-cross-section contact member constructed and arranged for movement into and out of engagement with said contact fingers at the one end of said assembly, a longitudinal groove formed in each of said contact fingers and opening toward said conductive member, a helically wound resilient current interchange spring disposed in each of the gaps between said grooves in said conductive member,

the outside convolutional diameter of each of said springs being greater than the distance between said groove and said conductive member so that each of said springs are forced to lay over with their individual convolutions inclined relative to their helical axis, the inherent resiliency of said springs holding each of their individual convolutions in firm electrical engagement with their associated contact fingers in said conductive member, whereby a plurality of current interchange paths are provided across said gaps and said contact fingers are urged into high pressure electrical engagement with said contact rod, said springs extending over a substantial portion of the length of said contact fingers, and a circular-in-cross-section spacer member disposed between said contact fingers and adjacent the other end of said contact assembly, said spacer member and said elongate contact rod supporting said contact fingers in substantial parallelism to insure uniform contact pressure between said springs and said contact fingers and said conductive member throughout the ength of each of said springs.

References Cited in the file of this patent UNITED STATES PATENTS 1,873,042 Rohrdanz Aug. 23, 1932 2,123,631 Koehler July 12, 1938 2,154,275 Linn Apr. 11, 1939 2,203,806 Wolf June 11, 1940 2,300,893 Hayford Nov. 3, 1942 2,449,479 Hopper et al Sept. 14, 1948 2,882,514 Krantz Apr. 14, 1959 FOREIGN PATENTS 511,967 Itaiy Jan. 28, 1955 OTHER REFERENCES German application, 1,042,137, Oct, 30, 1958. 

1. A CONTACT ASSEMBLY COMPRISING A PLURALITY OF ELONGATE CONTACT FINGERS, SAID CONTACT FINGERS EACH HAVING A CONTACT SURFACE ON ONE SIDE THEREOF, CERTAIN OF SAID CONTACT FINGERS BEING DISPOSED WITH THEIR CONTACT SURFACES IN AN OPPOSED RELATION TO EACH OTHER FOR RECEIVING AN ELONGATE CONTACT THEREBETWEEN, A CONDUCTIVE MEMBER DISPOSED IN SPACED RELATION FROM THE OPPOSITE SIDES OF EACH OF SAID CONTACT FINGERS, A HELICALLY WOUND RESILIENT CURRENT INTERCHANGE SPRING DISPOSED IN THE GAP BETWEEN EACH OF SAID CONTACT FINGERS AND SAID CONDUCTIVE MEMBER, THE AXIS OF SAID SPRINGS BEING PARALLEL TO THE LONGITUDINAL AXIS OF SAID CONTACT FINGERS, THE OUTSIDE CONVOLUTIONAL DIAMETER 